Anterior lumbar interbody fusion (ALIF) is a surgical procedure used to join two or more vertebrae. Interbody fusion includes removing an intervertebral disc and replacing the disc with an implant. The implant may be naturally occurring, for instance bone tissue, or it may be a non-naturally occurring substance, such as a plastic or plastic derivative. Often, supplementary bone tissue is used in conjunction with non-natural implants to fuse the vertebrae. Spinal fusion procedures are performed to alleviate pain due to abnormal motion of the vertebrae usually caused by degenerative conditions. However, spinal fusion is also the preferred way to treat spinal deformities.
In ALIF, the vertebral disc space is fused by approaching the spine through the abdomen instead of through the lower back. A three-inch to five-inch incision is made on the left side of the abdomen and the abdominal muscles are retracted to the side. The anterior abdominal muscle in the midline runs vertically and therefore does not need to be cut and easily retracts to the side.
Interbody spinal fusion places the implant between the vertebrae in the area usually occupied by the intervertebral disc. In preparation for the spinal fusion, the disc is removed entirely. A device may be placed between the vertebra to maintain spine alignment and disc height. After surgery, fusion occurs between the endplates of the vertebrae. Fusion is augmented by a process called fixation, where metallic screws, rods or plates, or cages are used to stabilize the vertebra and facilitate bone fusion.
Spinal implants generally have a structure which allows for the fusion of adjacent vertebral bodies by promoting growth of bone through the implant. The implant is sized to fit (both in length and width) in the space normally occupied by the vertebral disk. However, the size and shape of the implant is limited by the natural contours of the spine and the vertebral body. Present methods often involve drilling or cutting into the vertebrae in order to secure the implant. These procedures may weaken the vertebral structure and may contribute to failure of the implant. Therefore, one challenge encountered in spinal implant surgical procedures is manufacturing an implant that replicates the general dimensions of the intervertebral disk. An implant that matches the dimensions of the intervertebral disk will more securely reside in the disk space. Elimination, or at least minimization, of movement promotes faster and more efficient fusion with the vertebrae. It may therefore be advantageous to insert multiple implants of a smaller size into the vertebral disk area to insure a better fit. The size of the implants and the spacing of these multiple implants within the disk area will vary depending on the anatomy of the individual patient. What is needed in the art, therefore, is an anterior lumbar interbody fusion method and device which allow for custom spacing of multiple implants.